Abnormality detection device of chemical solution, liquid processing device, substrate processing apparatus, abnormality detection method of chemical solution, liquid processing method, and substrate processing method

A device includes a chemical solution flow path in which a chemical solution containing polymers flows; a laser beam irradiator configured to irradiate a laser beam to the chemical solution flow path such that an optical path is intersected with a flow direction of the chemical solution in the chemical solution flow path; a light receiving element provided in the optical path passing through the chemical solution flow path; a detector configured to detect, based on a signal output from the light receiving element, an abnormality in a state of polymers corresponding to a majority of the polymers contained in the chemical solution or configured to detect a ratio between a chemical solution containing the polymers and another chemical solution in the chemical solution flow path.